Current development status of rotary shaft lip seals

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The rotary shaft lip seal (abbreviated as oil seal) is a precision rubber sealing component with high technical complexity; it prevents the leakage of lubricating oil or other fluids by utilizing a flexible rubber (or leather, plastic, etc.) seal in contact with the shaft. In the early days, oil seals were made from leather. After World War II, the use of oil seals made from synthetic rubber increased gradually. Especially in the past two or three decades, due to the rapid development of industries such as machinery manufacturing, automotive, aviation, and aerospace, stringent requirements have been placed on oil seals: the ability to withstand high and low temperatures, high pressures, and special media, as well as the capacity to function under high speeds and vibrations while also having an extended service life. This has led to extensive and in-depth research into the materials used for oil seals, their structure, performance testing, quality control methods, and sealing mechanisms, **resulting in improved sealing performance and longer service life for these seals. In the early 1960s, fluid dynamic oil seals with a backflow effect were developed abroad, which brought about a significant advancement in seal technology and enabled the solution of sealing problems in some particularly difficult applications. In the 1980s, the United States developed polytetrafluoroethylene oil seals, which are suitable not only for ultra-high speeds but also for environments with extreme temperatures, as well as for exposure to various corrosive substances; they are also appropriate for use in situations involving dry friction. The introduction and implementation of international standards for oil seals in the 1980s further ensured their applicability and interchangeability on a global scale; various manufacturers began to revise their own standards by referring to these international standards. Our country started late in the field of oil seal research. Although significant progress has been made over the past decade or so, there is still a large gap compared to international standards in terms of product structure design, rubber compounding technology, production processes, manufacturing equipment, mold processing, and quality control methods. At present, the production of oil seals in our country is mostly carried out by small enterprises with relatively simple facilities. Outdated production processes and equipment, coupled with a lack of adequate understanding in terms of the high technical complexity and precision required for oil seals, as well as an underestimation of the complexity of performance requirements and the strictness of processing standards, along with insufficient investment, result in poor quality oil seals in China, unreliable sealing performance, and short service life. The production standards of most manufacturers remain at the level of foreign countries’ levels from the 1950s and 1960s. Most of the high-performance wind turbines in our country rely on imports. On the other hand, the poor quality of oil seals also affects the competitiveness of China’s mechanical products in the international market. Therefore, although oil seals account for a small proportion in the entire machinery industry, they are indeed a type of precision rubber seal that plays a significant role in the rubber industry – offering wide-ranging applications and a substantial impact, as well as bringing great social and economic benefits. They also contribute significantly to the development of the national economy, and thus their development deserves high attention. {:2_32:}